one type of tamper indicating closure, includes molded circumferentially spaced bridges in order to define a tamper indicating band on the closure. Such construction requires costly more complex molds which also require maintenance. Typical patents showing such tamper indicating closures comprise U.S. Pat. Nos. 4,613,052, 4,721,218, 4,801,031, 5,090,246 and 5,090,788.
Another type of tamper indicating closure comprises utilizing an interrupted edged knife to produce bridges such as shown in U.S. Pat. No. 4,322,009.
In another type of tamper indicating closure, circumferentially spaced axial bridges are provided on the internal surface of the skirt of the closure and a continuous straight edged knife is applied from the exterior surface cutting through the wall of the closure and into the bridges. Such a construction also requires costly complex molds that require maintenance and necessitates relatively thin walls on the closures. A typical patent showing such a construction comprises U.S. Pat. No. 4,545,496.
In United States application Ser. No. 08/048,638 filed Apr. 19, 1993, having a common assignee with the present application, a tamper indicating closure is shown which comprises a base wall and a peripheral skirt having an internal thread adapted to engage the threads of a container wherein a tamper indicating band is provided on the skirt by a plurality of circumferentially spaced bridges. The band includes portions adapted to engage an annular bead on the container. The bridges are formed by using a primary knife having an interrupted cutting edge to produce a circumferential score in the side wall of the closure leaving spaced connectors or bridges. A secondary knife is used having a continuous uninterrupted cutting edge to provide a continuous external score line to provide an accurately dimensional radial thickness of the bridges. In a preferred method and apparatus, the closures engage the successive primary and secondary knives and are moved such that the closures roll relative to the knives.
In such apparatus, each arcuate knife is mounted directly onto the apparatus, and its radial position and concentricity are set while the knife is mounted on the apparatus, using adjusting micrometer screws, one at each end of the arcuate blade. Such an apparatus has the disadvantage of loss of machine productive time while the operator is setting blades. It is also difficult to maintain knife concentricity with the center of rotation of the apparatus. This requires operator skill in setting of the Knives, and effective maintenance of the arcuate setting.
Among the objectives of the present invention are to provide a method and apparatus utilizing successive arcuate cutting knives wherein each knife blade is accurately set utilizing a remote setting fixture; wherein the setting fixture does not require the use of a dial indicator and, therefore, is not affected by the variability of the dial indicator setting and needs less skill in use; wherein the setting fixture cannot be over adjusted; and wherein the adjustment is less dependent on operator skill.
In accordance with the invention, a method and apparatus for scoring plastic tamper indicating closures to provide the tamper indicating band that is connected to the closure by bridges formed by scoring. The scoring is achieved by successively moving a rotating closure on rotating mandrel past a stationary primary knife blade having an arcuate concave interrupted cutting edge to form the bridges and then past a secondary knife blade having an arcuate concave uninterrupted cutting edge to accurately dimension the bridges. The method and apparatus provides for supporting each knife blade on a holder wherein the position of the blade can be set by setting the blade into a knife blade holder using a setting fixture remote from the apparatus, clamping the blade within the knife blade holder, transferring the holder to a machine mounting on the apparatus, then attaching the holder to the machine mounting without further adjustment, such that the arcuate knife blade is aligned such that the center of the radius of the arc of each arcuate knife blade is substantially coincident with the center of the apparatus. Each knife blade holder is preferably mounted on a slide on the rotary apparatus such that the arcuate edge can be finely adjusted so that the concave arc is parallel to the path of travel of the mandrels and at the required depth for the successive scoring.
The method and apparatus includes:
1. Remote setting of an arcuate knife blade using an adjustment knob with a built in torque limiter, to drive a cam which in turn moves a blade to a predetermined position against a fixed stop, with a controlled force. PA1 2. The provision of a machine slide having a mounting suitable for the knife blade such that the linear movement of the slide is radial to the center of rotation of a turret apparatus, clamping of an arcuate knife blade with a holder while the knife blade is securely held in a preset position, such that when transferred to the machine mounting, the arcuate knife blade will be aligned such that both the center of the radius of the arc of the arcuate knife blade and the midpoint of the arc lie on a radial line from the center of the turret apparatus parallel to the linear adjustment of said slide. PA1 3. Linear adjustment means by a micrometer screw on the machine, and position indication by digital indicator to enable minor changes in the depth of radial cut of the blade on the machine.